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Year : 2019  |  Volume : 24  |  Issue : 1  |  Page : 19-22

Prevalence and antibiotic resistance pattern of Metallo-β-lactamase-producing Pseudomonas aeruginosa isolates from clinical specimens in a tertiary care hospital

Department of Microbiology, SMS Medical College, Jaipur, Rajasthan, India

Date of Web Publication14-Mar-2019

Correspondence Address:
Dr. Nita Pal
82, Green Nagar, Durgapura, Jaipur - 302 018, Rajasthan
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jmgims.jmgims_23_18

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Background: Pseudomonas aeruginosa is emerging as a nosocomial pathogen by producing metallo-β-lactamases (MBLs) and acquiring resistance to many antimicrobial agents. The infections caused by metallo-beta-lactamases producing P. aeruginosa (MBL-PA) are associated with higher rates of mortality, morbidity, and overall healthcare costs. Aim: The aim of the study was to find the incidence of MBL in P. aeruginosa isolates and their antimicrobial resistance pattern. Material and Methods: A total of 180 non-duplicate P. aeruginosa isolates from various clinical specimens between April 2016 and March 2017 were subjected to susceptibility testing by disc diffusion test as per the Clinical and Laboratory Standards Institute guidelines 2015. Imipenem and meropenem resistant isolates were selected for the detection of MBL production by disc potentiation test and modified Hodge test. Results: Out of 180 isolates of P. aeruginosa, MBL was detected in 36 (20.00%) isolates. Resistance was significantly higher in the MBL-PA with 94.44% resistance to aztreonam followed by cefoxitin (91.66%), piperacilline/tazobactam and cefepime (80.55%). The prevalence of multidrug-resistant and possible extensively drug-resistant isolates was significantly higher among the MBL group as compared to that in the non-MBL group [50.00% vs. 11.11% and 5.55% vs. 0.69% (P = <0.05)]. None of the isolates were pan drug resistant. Conclusions: Increasing prevalence of MBL-PA producing isolates in hospital settings makes it important to perform routine detection of MBL strains for the purpose of infection control and for minimizing the adverse outcome of infection.

Keywords: Metallo-β-lactamase, multidrug resistance, Pseudomonas aeruginosa

How to cite this article:
Choudhary V, Pal N, Hooja S. Prevalence and antibiotic resistance pattern of Metallo-β-lactamase-producing Pseudomonas aeruginosa isolates from clinical specimens in a tertiary care hospital. J Mahatma Gandhi Inst Med Sci 2019;24:19-22

How to cite this URL:
Choudhary V, Pal N, Hooja S. Prevalence and antibiotic resistance pattern of Metallo-β-lactamase-producing Pseudomonas aeruginosa isolates from clinical specimens in a tertiary care hospital. J Mahatma Gandhi Inst Med Sci [serial online] 2019 [cited 2023 Mar 29];24:19-22. Available from: https://www.jmgims.co.in/text.asp?2019/24/1/19/254123

  Introduction Top

The genus Pseudomonas belongs to the family Pseudomonadaceae and consists of aerobic, Gram-negative, nonfermentative, nonsporing, and oxidase positive bacilli.[1] Pseudomonas aeruginosa is an important cause of nosocomial infections and causes infections ranging from urinary tract infection to severe sepsis.[2] For severe Pseudomonas infections, carbapenems are the antibiotics of choice, but resistance to carbapenem resistance is increasing worldwide mostly due to the production of metallo-β-lactamases (MBLs).[3] P. aeruginosa-producing MBL (MBL-PA) was first reported from Japan in 1991.[4] The present study was undertaken to find out the prevalence and antimicrobial resistance pattern of MBL-PA in our institution.

  Materials and Methods Top

The present study was carried out in the department of microbiology, from April 2016 to March 2017. A total of 180 nonlactose fermenting, oxidase positive, and Gram-negative bacilli isolated from various clinical specimens such as pus, blood, sputum, throat swab, ear swab, cerebrospinal fluid, urine, pleural fluid, and corneal swab were included in the study. The isolates were confirmed by Grams staining, biochemical tests, pigment production (chloroform test), and growth at 42°C.[1] Antibiotic susceptibility testing was done on Mueller–Hinton agar by Kirby–Bauer disc-diffusion method and the results interpreted as per the Clinical Laboratory Standards Institute 2015 criteria.[5] Antimicrobial susceptibility testing was done with gentamicin (10 μg), amikacin (30 μg), imipenem (10 μg), meropenem (10 μg), ceftazidime (30 μg), cefepime (30 μg), ciprofloxacin (5 μg), levofloxacin (5 μg), ticarcillin-clavulanic acid (75/10 μg), piperacillin-tazobactam (100/10 μg), aztreonam (30 μg), colistin (10 μg), and polymyxin B (300 unit).

  • Multidrug resistant (MDR) – Resistance to ≥1 agent in ≥3 antimicrobial categories
  • Extensively drug resistant (XDR) – Resistance to ≥1 agent in all but <2 categories
  • Pandrug resistant (PDR) – Resistance to all antimicrobial agents listed.[6]

Isolates showing resistance to imipenem and meropenem (inhibition zone <19 mm) by disc-diffusion method were considered as potential MBL producers and further confirmed by disc-potentiation test and modified Hodge test (MHT).[7]

Statistical analysis was done using computer software Primer. The qualitative data were expressed in proportion and percentages and the quantitative data were expressed as mean and standard deviations. The difference in proportion was analyzed using Chi-square test. Significance level for tests was determined as 95% (P < 0.05).

  Results Top

During the study period, a total of 180 isolates of P. aeruginosa were collected. Out of 180 isolates of P. aeruginosa, 61 (33.88%) were resistant to imipenem; MBL-PA was detected by disc potentiation test and MHT in 36 (20%) isolates. The demographic comparison of patients infected with MBL-PA and non-MBL-PA isolates is shown in [Table 1]. Out of 36 MBL-PA, 25 isolates (69.44%) were recovered from male patients and 11 isolates (30.55%) were recovered from female patients. Among 144 non-MBL-PA isolates, 87 (60.41%) were recovered from males and 57 (39.58%) were recovered from females. For both the groups, the isolates were obtained most commonly from the 21 to 40 year age group (41.66%), followed by the 41–60-year-age group (20%). There was no statistical difference between the mean age of patients for MBL-PA (33.85 ± 15.03 years) and non-MBL-PA (32.97 ± 17.95 years) isolates (P = 0.847). The most common specimen source for both MBL-producing and non-MBL-PA was pus (36.11% and 20.83%, respectively) [Table 2]. MBL-producing P. aeruginosa was isolated from 88.11% (32/36) inpatients and 11.11% (4/36) outpatients, while non-MBL-PA was obtained from 85.41% (123/144) inpatients and 14.58% (21/144) outpatients respectively (P = 0.788).
Table 1: Sex and age group distribution of metallo-β-lactamase and nonmetallo-β-lactamase producing Pseudomonas aeruginosa isolates

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Table 2: Distribution of metallo-β-lactamase and nonmetallo-β-lactamase producing Pseudomonas aeruginosa isolates among various specimens

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[Table 3] compares the results of antibiogram for routinely tested antipseudomonal agents of MBL-PA and non-MBL-PA isolates. The MBL-PA isolates showed highest resistance to aztreonam (94.44%) followed by cefoxitin (91.66%), piperacillin/tazobactam (80.55%), and cefepime (80.55%), while resistance among non-MBL-PA isolates was 79.86% to cefoxitin, 60.41% to aztreonam, 50.69% to cefepime 38.88% to cefoxitin, 38.88% piperacillin/tazobactam and 17.38% to imipenem. Resistance to all the antibiotics used in the study, except ticarcillin-clavulanic acid, aztreonam, polymyxin B, and colistin was significantly more in the MBL-PA strains, compared to that in the non-MBL-PA strains. The prevalence of MDR and possible XDR isolates was significantly higher among the MBL group as compared to that in the non-MBL group (50% vs. 11.11% and 5.55% vs. 0.69% (P = <0.05)] [Table 4]. None of the isolates were PDR.
Table 3: Antibiotic resistance pattern of metallo-β-lactamase and nonmetallo-β-lactamase producing Pseudomonas aeruginosa isolates

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Table 4: Prevalence of multidrug resistance and possible extensively drug resistance among metallo-β-lactamase and nonmetallo-β-lactamase producing Pseudomonas aeruginosa isolates

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  Discussion Top

The occurrence of MDR MBL-PA isolates in a hospital setting is of concern as it poses a problem in therapy and infection control management.[4] In our study, the prevalence of MBL-PA isolates was 20%, while in a previous study from the same hospital (2012), a prevalence of 18.37% was reported by Sachdeva et al.[8] Kumar et al.[9] reported a prevalence of 20% from the same region, while Agarwal et al.[10] reported a prevalence of 11.81%. In India, the prevalence rate of MBL-PA has been reported to vary from 11% to 25%. A similar prevalence rate of MBL-PA has been observed in various studies conducted by Kali et al.[11] (16.32%), Gupta et al.[12] (14.3%), Ranjan et al.[13] (16.72%), Chaudhary et al.[14] (16.89%), and Chauhan et al.[15] (19.15%). Compared to these findings, other studies have reported a lower prevalence of 5.5% by Thapa et al.,[16] 8.7% by Chaudhary et al.[14] 11.66% by Deeba et al.,[17] and 15.38% by Senthamarai et al.[18] Two studies from Uttarakhand[19] and Puducherry[20] reported higher prevalence of 38.6% and 50.5%, respectively. Variation in the detection rates of MBLs reported previously can be attributed to several factors that include geographical locations, infection control practices, number of samples tested, and methods used to detect MBLs.[17]

In the present study, MBL-PA was detected in 20% (36/180) isolates, of which 88.88% (32/36) isolates were from inpatients and 11.11% (4/36) were from outpatients. However, no significant difference was observed according to patient admission status between MBL-PA and non-MBL-PA (P = 0.788). Most of the studies have reported higher prevalence of MBL-PA isolates from inpatients.[10],[17],[21],[22]

In the present study, MBL-PA was predominantly isolated from pus 13 (36.11%), followed by endotracheal secretions 7 (30.43%) and urine 7 (19.44%). The same has been reported by Ranjan et al.,[13] Deeba et al.,[17] and Anuradha et al.,[22] while Chaudhary[14] observed MBL-PA isolates more from blood specimens. Male preponderance 112 (62.22%) was noted in this study. Similar observations were made by Senthamarai et al.[18] and Ranjan et al.[13] Only in one study from Nepal,[23] female preponderance of 55.17% was reported. Outdoor activity, personal habits, nature of work, and exposure to areas, which are inhabited by organisms could be the reasons for male preponderance. Majority of the isolates (41.66%) were obtained from patients between 21 and 40 years which is in accordance with other studies.[13],[18],[23]

Our study has illustrated that the MBL-PA strains were more resistant to commonly used antimicrobial agents. MBL-PA isolates showed the highest resistance to aztreonam (94.44%) followed by cefoxitin (91.66%), piperacillin/tazobactam, and cefepime (80.55%). Several studies have also highlighted greater resistance exhibited by MBL-PA strains toward almost all classes of antimicrobials, as compared to non-MBL-PA strains. Resistance to colistin among MBL-PA in the present study was 2.77%, while Anuradha et al.[22] reported no resistance and Kumar et al.[9] 5%. Deeba et al.[17] and Kumar et al.[9] observed no polymyxin B-resistant MBL-PA isolates, but in the present study, 2.77% isolates were resistant.

The prevalence of MDR isolates in our study was significantly higher in the MBL-PA (44.44%) as compared to the non-MBL-PA (5.55%) (P ≤ 0.05). A similar result was found in a study conducted by Ranjan et al.,[13] in which 55.17% of the MBL-PA strains were MDR, whereas 8.62% were non-MBL-PA. Ranjan et al.[13] reported PDR among 7.88% MBL-PA strains and 0.68% in non-MBL-PA strains; however, in the present study no PDR strains were isolated. The significantly higher prevalence of multidrug and possible XDR among MBLPA strains, as compared to that in non-MBL-PA strains, supports the notion that clinical microbiological laboratories must be able to distinguish MBL-PA strains from those with other mechanisms responsible for carbapenem resistance. The identification of MBL-PA isolates also has clinical implications, because such isolates are more likely to cause invasive disease and are associated with a higher hospital case fatality rate, compared with other imipenem-resistant isolates.[7],[13]

  Conclusion Top

Worldwide increase in the occurrence of MBL-PA is alarming. They also possess intrinsic resistance to many antibiotics, develop resistance by mutations, and participate in horizontal MBL gene transfer with other pathogens. Early detection is therefore crucial for the treatment with alternative antimicrobials and timely implementation of strict infection control practices. There is no standardized method for MBL detection, though detection by polymerase chain reaction is highly accurate and reliable, but its accessibility is often limited to reference laboratories. Thus, laboratory methods including culture and antimicrobial susceptibility testing with routine screening for MBL production should be done for proper diagnosis and management of all P. aeruginosa infections.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Table 1], [Table 2], [Table 3], [Table 4]

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